Problem: What is the amplitude of $g(x)=\cos\left(\dfrac{2\pi}{3} x\right)+1$ ?
Explanation: Amplitude in sinusoids of the form $f(x)=a\cos(bx+c)+d$ The amplitude of a sinusoid of the form $f(x)={a}\cos(bx + c) + d$ is equal to $|{a}|$. [How can we justify this given our graphical understanding of amplitude?] Finding the amplitude The amplitude of $g(x)={1}\cos\left(\dfrac{2\pi}{3} x\right)+1$ is $|{1}|=1$.